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Dosimetry Physics 1 > Concepts of Dose Calculations Pt. 1 > Flashcards

Concepts of Dose Calculations Pt. 1 Flashcards

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1
Q

Ionizing Radiation

A

Electromagnetic/particular radiation capable of producing ion pairs by interacting with matter

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2
Q

What are 6 examples of ionizing radiation?

A

X-rays, Gamma Rays, Alpha, Beta, Neutrons and Charged nuclei

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3
Q

What are the three IR interactions in radiotherapy?

A

Photoelectric, Compton and Pair Production

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4
Q

What is the unit of activity?

A

Ci and Bq

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5
Q

What is the unit of ionization in air?

A

R

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6
Q

What does KERMA stand for?

A

Kinetic Energy released in medium

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7
Q

What is the unit for absorbed dose?

A

Rad/Gy

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8
Q

What is the unit for dose equivalent?

A

Rem/Sv

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9
Q

1 Curie = ? Bq

A

3.7e10 dps

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10
Q

What is exposure? Unit?

A

the measure of ionization in the air. Roentgen

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11
Q

What is the equation for exposure?

A

exposure (X)= Charge(Q)/Mass (M)

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12
Q

What are 3 things exposure is defined by?

A

For photons, ionization of dry air, ionization at elect equilibrium

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13
Q

what is the SI for exposure?

A

2.58e-4 C/Kg

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14
Q

What is charge particle equilibrium

A

If a leaving charged particle is leaving, and replaced by another charged particle of the same type and same energy, then there is charged particle equilibrium (If a negative 21 keV electron leaves and another 21 keV neg electron comes in then its “normal”

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15
Q

What is the equation for KERMA?

A

KERMA= Kcol+Krad

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16
Q

What is Kcol?

A

part of energy lost due to collision with atoms, resulting in excitation or ionization

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17
Q

What is Krad?

A

energy lost in producing Bremsstrahlung photons

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18
Q

What is the greater component of KERMA?

A

Kcol

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19
Q

What is the equation of dose components?

A

Primary Beam + Sum of all scatterings

20
Q

What is radiation absorbed dose?

A

Amount of radiation absorbed within a material

21
Q

What are the units of Radiation absorbed dose?

A

1 Rad= 100 ergs/gram

22
Q

1 Gy = ?,?

A

100 cGy/Rad, 1 J/kg

23
Q

1 cGy =?

A

1 Rad

24
Q

The equation for absorbed dose?

A

Dose= Energy absorbed (directly or indirectly)/ mass of material

25
Q

f factor?

A

Conversion factor from Roentgen to cGy

26
Q

What are the two factors that affect the f Factor?

A

Density of the matter and the Beam energy

27
Q

Absorbed = ____ x Exposure?

A

f Factor

28
Q

What is the f Factor for dose in the air?

A

0.876

29
Q

What is the f Factor for dose in a medium?

A

0.956

30
Q

fmed= ?/?

A

Mass attenuation coeff in medium/mass attenuation coeff in air

31
Q

Dose equivalent equation?

A

H= Absorbed dose x quality factor

32
Q

What is the significance of H in the dose equivalent equation?

A

Takes into account the radiobiological effectiveness and depends on the dose and type of radiation

33
Q

What is the quality factor?

A

factor that compares biological effectiveness of a particulate form of radiation to a standard x-ray radiation

34
Q

H(?)=D(rad)x Quality factor

A

Rem and Rad

35
Q

What is the quality factor for photons, gamma ray, electrons?

A

1

36
Q

What is the quality factor for alpha particles?

A

20

37
Q

What is the quality factor for neutrons/protons?

A

10

38
Q

What is the 1st type of photon interaction?

A

The photon can penetrate through the matter without interacting

39
Q

What is the 2nd type of photon interaction?

A

The photon can be completely absorbed into matter and deposit its energy

40
Q

What is the 3rd type of photon interaction?

A

The photon can be scatters or deflect from original path and deposit some of its energy

41
Q

What is the electron build up region?

A

The region in which small deposits of the dose are made and built up until the point of maximum deposition of dose, known as Dmax

42
Q

What is Dmax?

A

Depth of maximum ionization, max absorbed dose occurring for a single photon fields

43
Q

What affects Dmax?

A

Beam Energy

44
Q

As BE increases, what occurs to Dmax?

A

Depth of Dmax increases

45
Q

Where does Dmax occur for LE? HE?

A

LE is on the surface of the skin and HE is beneath the skin

46
Q

What is the Dmax for Co-60, 4, 6, 10, 15, 18MV?

A
  1. 0.5
  2. 1.2
  3. 1.5
  4. 2.5
  5. 3.0
  6. 3.3

Dosimetry Physics 1 (6 decks)

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